Deformation correcting device

ABSTRACT

A deformation correcting device to correct a deformation occurring in a ring shaped article, which has been heated, while the heated ring shaped article is cooled, includes a support table, on which the ring shaped article in a heated condition is placed; a pair of receiving rolls; a press roll provided in opposition to the pair of the receiving rolls with the ring shaped article intervening therebetween; a press roll drive mechanism for driving the press roll between an advanced position, at which the press roll is urged against the outer peripheral surface of the ring shaped article, and a retracted position, at which the press roll is separated away from the outer peripheral surface of the ring shaped article; and a press roll rotating mechanism for rotating the press roll then urged against the ring shaped article by the press roll drive mechanism.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.12/733,853, filed on Mar. 24, 2010, which claims the benefit under 35U.S.C. Section 371, of PCT International Application NumberPCT/JP2008/002633, filed Sep. 24, 2008, which claimed priority toJapanese Application Nos. 2007-253288 filed Sep. 28, 2007, 2007-253289,filed Sep. 28, 2007, 2007-253290, filed Sep. 28, 2007 and 2007-265389,filed Oct. 11, 2007, the contents of which are incorporated herein byreference.

BACKGROUND

1. Field

The present invention relates to a method of quenching a ring shapedarticle such as, for example, a bearing raceway ring or the like, whichis performed while correction of a thermal deformation of the ringshaped article is carried out, and an apparatus accomplishing suchquenching.

2. Description of the Related Art

If such a ring shaped article as a raceway ring or the like of a bearingassembly is quenched, a deviation may occur in the circularity as aresult of thermal deformation. For this reason, after the quenching, aprocess of correcting such deformation is generally practiced with theuse of a ring shaped deformation correcting jig.

However, if correction of the deformation is carried out at a processstep separate from the step of quenching, the number of process steps inthe manufacturing line for the production of ring shaped articles willincrease and, therefore, as shown in FIG. 10, the deformation iscorrected when quenching by cooling the ring shaped article W insertedinto an arresting die 40. More specifically, after the ring shapedarticle W has been heated to a quenching temperature (about 850° C.),the ring shaped article W is cooled down to a temperature near to amartensitic transformation point (martensitic transformationtemperature: 230° C.) without being restrained in any arresting die;when it is cooled down to such temperature, the ring shaped article W isplaced inside the arresting die 40 and is then cooled down to apredetermined temperature (about 110° C.); after the ring shaped articleW has been cooled down to such temperature, the ring shaped article W isremoved from the arresting die 40; and thereafter the ring shapedarticle W is allowed to cool naturally down to room temperature.

Also, as one method of correcting the deformation with the use of thearresting die, the method has been suggested, in which using thearresting die of an axially elongated and vertically extendingcylindrical configuration, a ring shaped article then at a cooling stepof the quenching process is forcibly inserted into the verticallycylindrical arresting die sequentially from above so that the ringshaped article within the arresting die can be pushed sequentiallyoutwardly from below. For example, see Japanese Patent Publication No.H09-176740.

It has, however, been found that the deformation correcting methodutilizing the arresting die as hereinabove described requires thearresting die, which tends to incur a high manufacturing cost, to beprepared for each of ring shaped articles of different dimensions. Also,a work of mounting the ring shaped article in the arresting die and awork of removing the ring shaped article from the arresting die aftercompletion of the quenching require a substantial amount of labor. Inthe case of the deformation correcting method disclosed in JapanesePatent Publication No. H09-176740 referred to above, no work of removingthe ring shaped article from the arresting die is needed, but since inthis method, the ring shaped article is retained within the arrestingdie by the effect of a frictional force developed between the arrestingdie and the ring shaped article, there is the possibility that the ringshaped article of a large dimension tends to fall downwards from thearresting die by the effect of its own weight and, therefore, suchmethod is merely applicable to ring shaped articles of a relativelysmall dimension.

In view of the above, it has been desired to develop the technology bywhich without incurring any cost and a labor, thermal deformation ofring shaped articles of varying sizes can be corrected.

Also, a continuous heating furnace largely employed in the conventionalquenching apparatus has such problems that it requires the use of asubstantial length of the path of travel of an article to be heated inorder for the latter to be heated to a quenching temperature and thatthe equipment tends to become bulky in size. Accordingly, it has beendesired that the quenching method and the quenching apparatus, bothbased on the foregoing technology, require the heating time, which isshort, and heating facilities which are compact.

SUMMARY

An object of the present invention is to provide a method of, and anapparatus for, quenching a ring shaped article, in which thermaldeformation of the ring shaped article, which occurs as a result of thequenching treatment, can be corrected during the quenching treatment ofsuch ring shaped article; such correction of the thermal deformation canbe accomplished without substantially requiring a cost and a labor andcan be applied to ring shaped articles of varying sizes; the ring shapedarticle can be efficiently heated to the quenching temperature; therequired heating time is short; and the required equipment is compact.

A method of quenching a ring shaped article in accordance with thepresent invention includes a heating step of heating the ring shapedarticle to a quenching temperature; a primary cooling step of coolingthe ring shaped article, which has been heated to the quenchingtemperature, down to a deformation correction initiating temperature,which is higher than a martensitic transformation point; and a secondarycooling step of cooling the ring shaped article, which has been cooleddown to the deformation correction initiating temperature, down to atemperature lower than the martensitic transformation point by, while apair of receiving rolls are held in contact with an outer peripheralsurface of such ring shaped article for rotation about an axis ofrotation, which is parallel to a center of the ring shaped article,pressing a press roll, rotatable about an axis of rotation parallel tothe center of the ring shaped article, against the outer peripheralsurface of the ring shaped article from one side of the ring shapedarticle opposite to a point intermediate between the receiving rolls.The ring shaped article referred to above may be, for example, a racewayring employed in a bearing assembly.

According to this ring shaped article quenching method, during thesecond cooling step, while the pair of the receiving rolls are rotatablyheld in contact with the outer peripheral surface of the ring shapedarticle, the press roll then rotating is urged against the outerperipheral surface of the ring shaped articles from the opposite side ofthe receiving rolls, the ring shaped article is cooled. In view of thefact that the ring shaped article is turned between the receiving rollsand the press roll while sandwiching between the receiving rolls and thepress roll under a predetermined load, the deformation occurring in thering shaped article can be corrected with the circularity increasedconsequently. When the interval between the receiving rolls and thepress roll is adjusted, the apparatus can be suited to the ring shapedarticles of varying sizes. This deformation correction is performed withno use of any arresting die and, therefore, no cost is incurred inutilizing the arresting die and neither a work to mount the ring shapedarticle on the arresting die nor a work to remove the ring shapedarticle from the arresting die is required. Since the deformationcorrection is performed during the secondary cooling step, no extra stepfor the deformation correction need not be employed.

In the practice of the present invention, the heating step is carriedout by induction heating.

According to this construction, since during the heating step, heatingis performed by induction heating to the quenching temperature, therequired heating equipment can be compactized as compared with theheating performed by the use of a continuous heating furnace.

In the practice of the present invention, the heating step includes apreheating step of heating by induction heating the ring shaped articleto a predetermined preheating temperature near to the quenchingtemperature and a soaking step of heating the ring shaped article, whichhas been heated to the preheating temperature, to the quenchingtemperature within a continuous heating furnace.

According to this construction, since the ring shaped article is heatedto the quenching temperature with the use of the preheating step forheating by induction heating and the soaking step for heating within acontinuous heating furnace, the ring shaped article can be heated deepby induction heating in a matter of minutes with a good energyefficiency and, also, due to the use of the continuous heating furnace,the ring shaped article in its entirety can be soaked. Although the useis made of the continuous heating furnace, such continuous heatingfurnace is used only for the purpose of heating the ring shaped article,which has been preheated to a temperature near to the quenchingtemperature, to the quenching temperature, and, therefore, the heatingtime can be reduced considerably in contrast to that required to heatfrom room temperature and the path of transport, through which the ringshaped article is transported within the furnace, may be short and,therefore, resulting in reduction of the size of the equipment.

In the practice of the present invention, an oil bath for cooling thering shaped article during the primary cooling step and an oil bath forcooling the ring shaped article during the secondary cooling step may beused separately.

The separate use of the cooling oil bath in the primary cooling step andthe cooling oil bath in the secondary cooling step is advantageous inthat the cooling of the ring shaped article during the primary coolingstep, loading of the ring shaped article in between the pair of thereceiving rolls and the press roll and the cooling of the ring shapedarticle during the secondary cooling step can be performed continuouslyin series with each other. Also, the quenching process line can bedesigned in a simple configuration.

The length of time during which the press roll is urged against theouter peripheral surface of the ring shaped article is preferably withinthe range of 40 to 90 seconds. Also, the temperature of the ring shapedarticle at the time a deformation correction is initiated with the pressroll urged against the outer peripheral surface of the ring shapedarticle is preferably 20° C. to 50° C. higher than the martensitictransformation point.

As a result of a series of tests conducted, it has been found that thelength of time during which the deformation correction is carried outwith the press roll urged against the outer peripheral surface of thering shaped article is preferred within the range of 40 to 90 seconds.Also, in order to complete the deformation correction during the coolingstep for quenching while the above described length of time during whichthe deformation correction is carried out is secured, it has been foundpreferred that urging of the press roll has to be initiated from thetemperature that is 20° C. to 50° C. higher than the martensitictransformation point.

An apparatus for quenching a ring shaped article according to thepresent invention includes a heating station for heating the ring shapedarticle to a quenching temperature; a primary cooling station forcooling the ring shaped article, which has been heated to the quenchingtemperature by the heating station, down to a deformation correctioninitiating temperature, which is higher than a martensitictransformation point; and a secondary cooling station for cooling thering shaped article, which has been cooled down to the deformationcorrection initiating temperature by the primary cooling station, downto a temperature lower than the martensitic transformation point by,while a pair of receiving rolls are held in contact with an outerperipheral surface of such ring shaped article for rolling motion aboutan axis of rotation, which is parallel to a center of the ring shapedarticle, pressing a press roll, rotatable about an axis of rotationparallel to the center of the ring shaped article, against the outerperipheral surface of the ring shaped article from one side of the ringshaped article opposite to a point intermediate between the receivingrolls.

According to this ring shaped article quenching apparatus, the ringshaped article is cooled at the secondary cooling station in a conditionin which while the pair of the receiving rolls are rotatably held incontact with the outer peripheral surface of the ring shaped article,the press roll then rotating is urged against the outer peripheralsurface of the ring shaped article from the opposite side. In view ofthe fact that the ring shaped article is turned between the receivingrolls and the press roll while sandwiching between the receiving rollsand the press roll under a predetermined load, the deformation occurringin the ring shaped article can be corrected with the circularityincreased consequently. When the interval between the receiving rollsand the press roll is adjusted, the apparatus can be suited to the ringshaped articles of varying sizes. This deformation correction isperformed with no use of any arresting die and, therefore, no cost isincurred in utilizing the arresting die and neither a work to mount thering shaped article on the arresting die nor a work to remove the ringshaped article from the arresting die is required. Since the deformationcorrection is performed during the secondary cooling step, no extra stepfor the deformation correction need not be employed.

In this ring shaped article quenching apparatus of the presentinvention, the heating station is operable to perform an inductionheating.

According to this construction, since at the heating station, heating isperformed by induction heating to the quenching temperature, therequired heating equipment can be compactized as compared with theheating performed by the use of a continuous heating furnace.

In this ring shaped article quenching apparatus of the presentinvention, the heating station includes a preheating station for heatingby induction heating the ring shaped article to a predeterminedpreheating temperature near to the quenching temperature and a soakingstation for heating the ring shaped article, which has been heated tothe preheating temperature, to the quenching temperature within acontinuous heating furnace.

According to this construction, since the ring shaped article is heatedto the quenching temperature with the use of the preheating station, atwhich heating by induction heating takes place, and the soaking station,at which heating takes place within a continuous heating furnace, thering shaped article can be heated deep by induction heating in a matterof minutes with a good energy efficiency and, also, due to the use ofthe continuous heating furnace, the ring shaped article in its entiretycan be soaked. Although the use is made of the continuous heatingfurnace, such continuous heating furnace is used only for the purpose ofheating the ring shaped article, which has been preheated to atemperature near to the quenching temperature, to the quenchingtemperature, and, therefore, the heating time can be reducedconsiderably in contrast to that required to heat from room temperatureand the path of transport, through which the ring shaped article istransported within the furnace, may be short and, therefore, resultingin reduction of the size of the equipment.

In a preferred embodiment of the present invention, the secondarycooling station of the ring shaped article quenching apparatus referredto above makes use of a ring shaped article deformation correctingdevice for correcting a deformation of the ring shaped article while thering shaped article once heated is cooled, which device includes asupport table, on which the ring shaped article in a heated condition isplaced; a pair of receiving rolls, which rollingly contact an outerperipheral surface of the ring shaped article on the support table; apress roll provided in opposition to the pair of the receiving rollswith the ring shaped article intervening therebetween; a press rolldrive mechanism for driving the press roll between an advanced position,at which the press roll is urged against the outer peripheral surface ofthe ring shaped article, and a retracted position, at which the pressroll is separated away from the outer peripheral surface of the ringshaped article; and a press roll rotating mechanism for rotating thepress roll then urged against the ring shaped article by the press rolldrive mechanism.

According to this ring shaped article deformation correcting device,since the correction of deformation is performed during the cooling stepfor quenching, the deformation correcting device can be disposed withoutincreasing the number of process steps of the manufacturing line for thering shaped article.

In the deformation correcting device, it is recommended to use a rollinterval adjusting mechanism for adjusting the interval between thereceiving rolls. If the interval between the receiving rolls of thatpair is adjustable, it is possible to render the apparatus to suit to afurther varying size of the ring shaped article.

In the deformation correcting device, it is recommended to use an oilbath for cooling purpose and a deformation correcting time coolingmechanism for immersing the ring shaped article into a quenching oil,contained within the oil bath, at the time of deformation correction tothereby cool the ring shaped article. For example, the deformationcorrecting time cooling mechanism may include a support unit fortiltably supporting the support table such that a ring shaped articlesupport area of the support table, where the ring shaped article isplaced, may be lowered, and a tilting unit for tilting the support tablesupported by the support unit, so that when the support table is tiltedby the tilting unit, the ring shaped article can be immersed into thequenching oil within the oil bath.

The provision of the deformation correcting time cooling mechanism iseffective to allow the ring shaped article to be corrected to remove thedeformation while being sufficiently cooled. If the deformationcorrecting time cooling mechanism is made up of the support unit and thetilting unit, the ring shaped article can be assuredly immersed into thequenching oil contained within the oil bath to cool it even though it isa simplified construction.

BRIEF DESCRIPTION OF THE DRAWINGS

In any event, the present invention will become more clearly understoodfrom the following description of preferred embodiments thereof, whentaken in conjunction with the accompanying drawings. However, theembodiments and the drawings are given only for the purpose ofillustration and explanation, and are not to be taken as limiting thescope of the present invention in any way whatsoever, which scope is tobe determined by the appended claims. In the accompanying drawings, likereference numerals are used to denote like parts throughout the severalviews, and:

FIG. 1 is a diagram showing a conceptual construction of a quenchingapparatus that is employed in executing a method of quenching a ringshaped article according to a first preferred embodiment of the presentinvention;

FIG. 2A is a top plan view showing a deformation correcting deviceemployed in the quenching apparatus;

FIG. 2B is a front elevational view showing the deformation correctingdevice shown in FIG. 2A;

FIG. 3 is an explanatory diagram showing the amount of change in outerdiameter of the ring shaped article;

FIGS. 4A and 4B are explanatory diagrams showing the amount of change inwall thickness of the ring shaped article;

FIG. 5 is a diagram showing a conceptual construction of the quenchingapparatus used to execute the method of quenching the ring shapedarticle according to a second preferred embodiment of the presentinvention;

FIG. 6 is a front elevational view, with a portion cut out, showing aninduction heating device employed at a preheating station in thequenching apparatus;

FIG. 7A is an explanatory diagram showing a first example of adjustingthe position of a heating coil employed in the induction heating device;

FIG. 7B is an explanatory diagram showing a second example of adjustingthe position of the heating coil;

FIG. 8A is a perspective view showing the heating coil;

FIG. 8B is a perspective view showing a different heating coil;

FIG. 9 is a diagram showing a conceptual construction of the quenchingapparatus used to execute the method of quenching the ring shapedarticle according to a third preferred embodiment of the presentinvention; and

FIG. 10 is an explanatory diagram showing the conventional deformationcorrecting method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A method of quenching a ring shaped article according to a firstpreferred embodiment of the present invention will be described withparticular reference to FIGS. 1 and 2A and 2B, which illustrate anapparatus used to execute such quenching method. Referring first to FIG.1, the quenching apparatus for quenching the ring shaped article isgenerally identified by 30 and includes a heating station 31, a primarycooling station 32, a secondary cooling station 33, and a cleansingstation 34. The heating station 31 makes use of a heating furnace or thelike to heat the ring shaped article W to a quenching temperature (forexample, 850° C.) (a heating step S1). The primary cooling station 32 isfor primarily cooling the ring shaped article W, which has been heatedto the quenching temperature, down to a temperature (for example, 290°C.), which is higher than the martensitic transformation point, byimmersing such ring shaped article W within a quenching oil contained ina primary cooling bath 32 a (a primary cooling step S2). The secondarycooling station 33 is for secondarily cooling the ring shaped article W,which has been primarily cooled, down to a predetermined temperature(for example, 110° C.) by immersing a quenching oil, contained in an oilbath 20, while a deformation correction is performed by means of adeformation correcting device 1 (a secondary cooling step S3). Thecleansing station 34 is for cleansing the ring shaped article W, whichhas been secondarily cooled, and then transferring it to the subsequentprocessing step.

In the practice of this first preferred embodiment, the primary coolingbath 32 a of the primary cooling station 32 has an oil accommodatingportion of a U-shaped sectional shape having opposite ends that definean introducing area 32 aa and a delivery area 32 ab, respectively, whichoil accommodating portion is so designed that the ring shaped article Wcan be transported from the introducing area 32 aa at one end thereoftowards the delivery area 32 ab at the opposite end thereof by means ofan elevator 32 b. A space 32 c above the introducing area 32 aa isrendered to be a closed space filled with a nitrogen gas N₂. Anopen/close door 32 d is provided between the space 32 c and the heatingstation 31. According to the construction of this primary cooling bath32 a, the ring shaped article W heated by the heating station 31 isimmediately loaded into the space 32 c; filled with the nitrogen gas N₂and is subsequently immersed into the quenching oil, and, accordingly,the cooling can be readily performed without the ring shaped article Wbeing exposed to the atmosphere.

As shown in FIGS. 2A and 2B, the deformation correcting device 1 of thesecondary cooling station 33 includes a support table 2 for the supportof the ring shaped article W thereon, and a pair of receiving rolls 3and a press roll 4 mounted on the support table 2. The receiving rolls 3are rotatably mounted on respective support shafts 3 a protrudingupwardly from associated receiving roll support members 7. The pressroll 4 is mounted on a press roll support shaft 4 a for rotationtogether therewith, which shaft 4 a protrudes upwardly from a press rollsupport member 11 and is rotatable relative to such press roll supportmember 11. The ring shaped article W is in the form of, for example, araceway member of a bearing assembly. The raceway ring of the bearingassembly is that formed by means of a forging process and has an innerperipheral surface or an outer peripheral surface formed with a racewaygroove by means of a grinding process. Material for the bearing racewayring may is, for example, a steel material such as, for example, abearing steel.

A portion of the top surface of the support table 2 between the pair ofthe receiving rolls 3 and the press roll 4 is designed as a ring shapedarticle support area 5 and a region thereof ranging from one to theother of opposite ends in a direction (Y-axis direction) of arrangementof the receiving rolls 3 is so formed as to lie at a level higher thanthat of the other portion thereof. This ring shaped article support area5 is formed with a cutout 5 a for the purpose of avoiding aninterference thereof with the press roll 4 and the press roll supportmember 11 when the press roll 4 is advanced as will be described later.In the neighborhood of the support table 2, there is provided a loadingand discharging mechanism (not shown) for loading the ring shapedarticle W onto the ring shaped article support area 5 from a directionshown by the arrow A and discharging the ring shaped article W from thering shaped article support area 5 towards a direction shown by thearrow B.

The pair of the receiving rolls 3 are spaced a distance in the Y-axisdirection from each other, which distance can be adjusted by a receivingroll interval adjusting mechanism 6 employed in association with each ofthe receiving rolls 3. The receiving roll interval adjusting mechanism 6includes the receiving roll support member 7, on which the respectivereceiving roll 3 is rotatably mounted, a guide 8 for displaceablyguiding the receiving roll support member 7 relative to the supporttable 2 in the Y-axis direction, and a fixing unit 9 for fixing thereceiving roll support member 7 to the support table 2. For this fixingunit 9, for example, a bolt or any fixing jig for fastening by theutilization of a frictional force can be employed.

The press roll 4 is adapted to be driven between advanced and retractedpositions by a press roll drive mechanism 10 in a direction (X-axisdirection) along a path passing through a point M intermediate betweenthe receiving rolls 3 and then through the longitudinal axis O of thepress roll 4. The press roll drive mechanism 10 includes the press rollsupport member 11 for rotatably supporting the press roll 4 ashereinbefore described, X-axis direction guide rods 12 along whichrespective to-be-guided elements 11 a, mounted on the press roll supportmember 11, are mounted for movement relative thereto, and a drive unit13 for driving the press roll support member 11 in the X-axis directionrelative to the support table 2. The to-be-guided elements 11 a serve toguide the associated guide rods 12 by the effect of, for example, asliding guide or a rolling guide. The drive unit 13 is comprised of, forexample, a hydraulic cylinder.

The press roll 4 is also adapted to be rotated by a press roll rotatingmechanism 15 in a predetermined direction. This press roll rotatingmechanism 15 is of a structure, in which a rotating motor 16 is mountedon the press roll support member 11 and a drive chain 19 is trainedbetween a sprocket 17, mounted on an output shaft of the rotating motor16, and a sprocket 18 mounted on the support shaft of the press roll 4.

As best shown in FIG. 2B, an oil bath for cooling the ring shapedarticle is disposed below the ring shaped article support area 5 of thesupport table 2, and the ring shaped article W resting on the ringshaped article support area 5 can be immersed into the quenching oilcontained in this oil bath 20. A deformation correcting time coolingmechanism 21 therefor is made up of a support unit 22 for supporting thesupport table 2 so that one side of the support table 2 adjacent thering shaped article support area 5 can be tiltably lowered, and atilting unit 23 for tilting the support table 2 supported by thissupport unit 22. In the illustrated embodiment, the support unit 22 isof a structure, in which a horizontally extending tilt center shaft 22a, protruding outwardly from opposite Y-axis direction sides of thesupport table 2 can be rotatably supported by corresponding pivotsupport members 22. Also, the tilting unit 23 is comprised of ahydraulic cylinder provided between a lower surface of the support table2, positioned on one side of the tilt center shaft 22 a opposite to thering shaped article support area 5, and a floor surface 24. As shown bythe solid line in FIG. 2B, when the support table 2 is tilted by thedrive of the tilting unit 23, the ring shaped article W resting on thering shaped article support area 5 can be immersed into the oil withinthe oil bath 20.

The deformation correction, accomplished by the deformation correctingdevice 1 at the secondary cooling station 33 shown in FIG. 1, will nowbe described with particular reference to FIGS. 2A and 2B. Thedeformation correcting device 1 is held standby at a retracted positionP1 with the press roll 4 having been retracted relative to the receivingrolls 3 as shown by the chain line in FIG. 2A. At this time, the supporttable 2 is held in a horizontal condition. The ring shaped article W,shown by the chain line and emerging outwardly from the primarilycooling bath 32 a shown in FIG. 1, is loaded on the ring shaped articlesupport area 5 of the deformation correcting device 1, then held standbyas described above, from a direction shown by A by the action of theloading and discharging mechanism (not shown). When the ring shapedarticle W is so loaded, as shown by the solid line in FIG. 2A, the driveunit 13 of the press roll drive mechanism 10 is driven to advance thepress roll 4 to an advanced position P2. In this way, as shown by thesolid line in FIG. 2A, the ring shaped article W is held by the pair ofthe receiving rolls 3 and the press roll 4 with its outer peripheralsurface restrained from both sides of the X-axis direction. In thiscondition, the rotating motor 16 of the press roll rotating mechanism 15shown in FIG. 2A is driven to rotate the press roll 4 in thepredetermined direction. While the ring shaped article W is restrainedunder a predetermined load by the pair of the receiving rolls 3 and thepress roll 4 from the opposite sides, the ring shaped article W isrotated between the rolls 3 and 4 so that a deformation can be correctedto allow the ring shaped article W to have an increased circularity.

Also, about the time of initiation of the above described deformationcorrection, that is, initiation of rotation of the press roll 4, asshown by the solid line in FIG. 2B, the tilting unit 23 of thedeformation correcting time cooling mechanism 21 is driven to tilt thesupport table 2 with the ring shaped article support area 5 loweredconsequently. Accordingly, the ring shaped article W is immersed intothe quenching oil contained in the oil bath 20 and is thereforesecondarily cooled. Since loading of the ring shaped article W onto thering shaped article support area 5, advance of the press roll 4,rotation of the press roll 4 and tilting of the support table 2 takeplace continuously, the primary cooling and the secondary cooling areperformed with no substantial time spent therebetween. For this reason,quenching takes place favorably.

The temperature of the ring shaped article W at the time the deformationcorrection is initiated with the press roll 4 urged against the outerperipheral surface of the ring shaped article W is chosen to be atemperature 20° C. to 50° C. higher than the martensitic transformationpoint. It is to be noted that the time of deformation correction is tobe construed as meaning the time span between the time, at whichpressing by the press roll 4 is initiated, and the time at which it iscompleted. Also, the length of time during which the deformationcorrection is carried out with the outer peripheral surface of the ringshaped article W urged by the press roll 4, is chosen to be about 40 to90 seconds. When the ring shaped article W of the above describedtemperature is immersed only for the above described length of time intothe quenching oil within the oil bath 20, the ring shaped article W iscooled down substantially to a target cooling temperature (for example,110° C.) of the secondary cooling. Accordingly, with no waste of time,the deformation correction and the secondary cooling are carried out.Upon completion of the deformation correction and the secondary cooling,the support table 2 is again returned to the initial, horizontalcondition and the rotation of the press roll 4 is halted, followed byretraction of the press roll 4 back to the retracted position P1, atwhich time the ring shaped article W is released. The ring shapedarticle W so released is, by the action of the loading and dischargingmechanism (not shown), discharged in a direction, shown by B in FIG. 2A,from the ring shaped article support area 5 of the support table 2 tothe outside of the support table 2.

The deformation correcting device 1 of the construction described abovedesigned for the ring shaped article is such that since the press roll 4can be selectively movable between the advanced and retracted positions,the distance between the pair of the receiving rolls 3 and the pressroll 4 can be changed as desired. For this reason, it can be applied toring shaped articles W of any varying diameters. The spacing between thereceiving rolls 3 may be changed by the receiving roll intervaladjusting mechanism 6 to suit to the size of the ring shaped article W.The deformation correction of the ring shaped article W by thedeformation correcting device 1 require no allowance for a die, since noarresting die is utilized, and, also, no work is required to mount thering shaped article W onto the die nor remove it from the die.

The quenching apparatus 30 of the present invention is such that sincethe deformation correction is carried out during the secondary coolingstep S3 by the deformation correcting device 1 of the secondary coolingstation 33, there is no need to provide an extra step of deformationcorrection. Since the primary cooling oil bath 32 a of the primarycooling station 32 and the secondary cooling oil bath 20 of thesecondary cooling station 33 are separate from each other, it ispossible to consecutively perform the cooling of the ring shaped articleW at the primary cooling station 32, the loading of the ring shapedarticle W in between the pair of the receiving rolls 3 and the pressroll 4, and the cooling of the ring shaped article W at the secondarycooling station 33. Also, the processing line of the quenching apparatus30 can be simplified in structure.

In order to ascertain the effect of deformation correction carried outduring the secondary cooling step S3 at the secondary cooling station 33of the quenching apparatus 30 of the structure described above, a seriesof tests were conducted. During the series of the tests, ring shapedarticles each made of a bearing steel and having a size of 280 mm indiameter, 250 mm in inner diameter and 15 mm in wall thickness. Withrespect to each of those ring shaped articles, the amount of change inouter diameter ΔD and the amount of change in wall thickness ΔT weremeasured by stepwise varying the pull-up temperature of the primarycooling and the press load of the press roll 4 in a plurality of stages.The amount of change in outer diameter ΔD represents the differencebetween the outer diameter D1 before the deformation correction and theouter diameter D2 after the deformation correction (FIG. 3). The amountof change in wall thickness ΔT represents the difference between thewall thickness T1 before the deformation correction and the wallthickness T2 after the deformation correction (FIGS. 4A and 4B). Foreach of the amounts of change in outer diameter ΔD and the amounts ofchange in wall thickness ΔT, the average value x, the standard deviationvalue a and the maximum value Max were determined. Results of thosetests are tabulated in Table 1 below.

TABLE 1 230° C. 250° C. 280° C. Load X σ Max x σ Max x σ Max 150 Amt. of1.37 0.47 1.88 0.21 0.16 0.40 0.22 0.11 0.42 kgf Outer Dia. Change ΔDAmt. of 0.16 0.02 0.19 0.31 0.01 0.33 0.30 0.03 0.32 Wall Thic. ChangeΔT 300 Amt. of — — — 0.16 0.08 0.25 0.16 0.03 0.22 kgf Outer Dia. ChangeΔD Amt. of — — — 0.28 0.13 0.36 0.30 0.03 0.35 Wall Thic. Change ΔT 580Amt. of 0.25 0.12 0.35 — — — 0.12 0.03 0.14 kgf Outer Dia. Change ΔDAmt. of 0.18 0.07 0.24 — — — 0.34 0.03 0.37 Wall Thic. Change ΔT

The results of the tests have revealed as follows.

(1) Regarding the amount of change in outer diameter ΔD, when theprimary cooling pull-up temperature was 250° C. and 280° C. and thepress load was 300 kgf, an excellent result could be obtained. Also,even when the primary cooling pull-up temperature was 280° C. and thepress load was 580 kgf, an excellent result could be obtained.

(2) Regarding the amount of change in wall thickness ΔT, when theprimary cooling pull-up temperature was 230° C., 250° C. and 280° C. andthe press load was 150 kgf, when the primary cooling pull-up temperaturewas 250° C. and 280° C. and the press load was 300 kgf, and when theprimary cooling pull-up temperature was 230° C. and the press load was580 kgf, respective excellent results could be obtained.

(3) From the foregoing, it has been ascertained that the excellentresults in the amount of change in outer diameter ΔD and the amount ofchange in wall thickness ΔT can be obtained when the primary coolingpull-up temperature is 250° C. and 280° C. and the press load is 300kgf.

The method of quenching the ring shaped article according to a secondpreferred embodiment of the present invention will be described withparticular reference to FIGS. 5 to 8A and 8B, which illustrate theapparatus used to execute such quenching method. The second preferredembodiment is basically similar in structure to that according to thepreviously described first embodiment except that heating performed bythe heating station 31 used during the heating step S1 in the practiceof the previously described first embodiment is carried out by means ofinduction heating. Accordingly, component parts employed in the secondembodiment, but similar to those in the first embodiment are shown bylike reference numerals and the details are not therefore reiterated forthe sake of brevity. As shown in FIG. 5, the ring shaped articlequenching apparatus 30 employed in the practice of the second embodimentof the present invention includes a pre-cleansing station 34A, a heatingstation 31, a primary cooling station 32, a secondary heating station 33and a post-cleansing station 34B.

At the pre-cleansing station 34A, swarfs and oil content, which adhereto the ring shaped article W during a turning process, are cleansed off.At the heating station 31, the ring shaped article W, which has beenpre-cleansed at the pre-cleansing station 34A, is heated by inductionheating to a predetermined quenching temperature (for example, 850° C.)by an induction heating device 50 (a heating step S1). At the primarycooling station 32, in a manner similar to that in the previouslydescribed first embodiment, the ring shaped article W, which has beenheated to the quenching temperature, is immersed in the quenching oilcontained in the primary cooling bath 32 a so that the ring shapedarticle W can be primarily cooled down to a temperature (for example,290° C.) that is higher than the martensitic transformation point (aprimary cooling step S2). At the secondary cooling station 33, the ringshaped article W, which has been primarily cooled, is immersed into thequenching oil within the oil bath 20 while deformation thereof iscorrected by the deformation correcting device 1, so that the ringshaped article W can be secondarily cooled down to a predeterminedtemperature (for example, 110° C.) (a secondary cooling step S3). At thepost-cleansing station 34B, the ring shaped article W, which has beensecondarily cooled, is transferred to the subsequent processing step.

The structure of the induction heating device 50 of the heating station31 is best shown in FIG. 6. This induction heating device 50 includes arotary table 51 for turning a ring shaped article W, placed on suchrotary table 51, about a ring center O1, a heating coil 52 and analternating current power source 53 for supplying an electric current tothe heating coil 52. The alternating current power source 53 is renderedto be, for example, a high frequency power source. A heating chamber 37,in which the induction heating device 50 is installed, is of anatmosphere filled with a nitrogen gas N₂.

The heating coil 52 is of a downwardly oriented U-shaped configurationstructured so as to straddle between inner and outer peripheral sides ofthe ring shaped article W as best shown in, for example, FIGS. 6 and 7Aand 7B. Opposite arms 52 a and 52 b of the heating coil 52 have theirfree ends connected across the alternating current power source 53. FIG.8A illustrates a perspective view of the heating coil 52 shown in FIGS.6 and 7A and 7B.

For the heating coil 52, such a structure may be employed, in which asbest shown in FIG. 8B, two U-shaped conductors 65 and 66 are so arrangedas to permit their leg conductors 65 a, 65 b, 66 a and 66 b to extendparallel to each other, one of the leg conductors 65 a and 66 a havetheir free ends connected with each other through a connecting conductor67, and the other of the leg conductors 65 b and 66 b have their freeends provided with respective lead portions 65 c and 66 c, which are inturn connected across the alternating power source 53.

Referring to FIG. 6, the heating coil 52 is so arranged that theposition thereof can be adjustable in a direction radially of the rotarytable 51 relative to a heating coil support body 54. The heating coilsupport body 54 includes, for example, a guide rod 54 a extending in adirection radially of the rotary table 51, and the heating coil 52 canbe adjusted in position continuously along this guide rod 54 a. At anarbitrary adjusted position, the heating coil 52 is fixed in position tothe guide rod 54 a by means of, for example, a bolt (not shown) or thelike. Thus, since the position of the heating coil 52 is adjustable, theposition of the heating coil 52 can be changed to suit to a relativelysmall ring shaped article W as is the case with a first example shown inFIG. 7A, or the position of the heating coil 42 can be changed to suitto a relatively large ring shaped article W as is the case with a secondexample shown in FIG. 7B.

A contact pedestal 51 a is provided in the rotary table 51 for thepurpose of reducing the surface area of contact with the ring shapedarticle W. This contact pedestal 51 a is rendered to be replaceable withanother one depending on the diameter of the ring shaped article W.

The rotary table 51 is rotationally driven by a rotary table rotatingdevice 55 and can be also moved by a rotary table elevating device 56between a position, at which the ring shaped article W placed on therotary table 51 enters in between the opposite arms 52 a and 52 b of theheating coil 52, and a position in which such ring shaped article Wdeparts from a space between the opposite arms 52 a and 52 b of theheating coil 52.

In the example as shown, the rotary table 51 is rotatably provided on anelevating frame 57 through bearings 58, and the elevating frame 57 isarranged on a base support 59 through an elevation guide member 60 formovement up and down along the elevation guide member 60. The elevatingframe 57 is drivingly coupled with an elevating drive source 61 such as,for example, a hydraulic cylinder and, accordingly, the rotary table 51is moved up and down by the elevating drive source 61 together with theelevating frame 57.

The rotary table rotating device 55 is made up of a motor 62 and arotation transmitting mechanism 63 such as, for example, pulleys or agear train for transmitting the rotation of the motor 62 to a shaft 51 bof the rotary table 51.

As hereinabove described, in the second embodiment of the presentinvention, since during the heating step S1, the ring shaped article isinduction heated by the induction heating device 50 at the heatingstation 32 to the quenching temperature, the heating facility can becompactized as compared with the heating with the use of a continuousheating furnace. Other functions and effects are similar to thoseafforded by the previously described first embodiment.

The method of quenching the ring shaped article according to a thirdpreferred embodiment of the present invention will be described withparticular reference to FIG. 9, which illustrates the apparatus used toexecute such quenching method. The third preferred embodiment isbasically similar in structure to that according to the previouslydescribed first embodiment, except that the heating step S employed inthe practice of the previously described first embodiment is dividedinto two steps, i.e., a preheating step S1A, including a preheatingstation 31A, and a soaking step S1B including a soaking station 31B.Accordingly, component parts employed in the third embodiment, butsimilar to those in the first embodiment may be occasionally shown bylike reference numerals and the details are not therefore reiterated forthe sake of brevity. As shown in FIG. 9, the ring shaped articlequenching apparatus 30 according to this third preferred embodimentincludes a pre-cleansing station 34A, a preheating station 31A, asoaking station 31B, a primary cooling station 32, a secondary coolingstation 33 and a post-cleansing station 34B.

At the pre-cleansing station 34A, swarfs and oil content, which adhereto the ring shaped article W during a turning process, are cleansed off.At the heating station 31A, the ring shaped article W, which has beenpre-cleansed at the pre-cleansing station 34A, is heated by inductionheating to a predetermined preheating temperature, which is near to thequenching temperature, by an induction heating device 50 (a heating stepS1A). At the soaking station 31B, the ring shaped article W, which hasbeen heated to the preheating temperature, is heated to a predeterminedquenching temperature (for example, 850° C.) within the continuousheating furnace 31 a (a soaking step S1B). At the primary coolingstation 32, the ring shaped article W, which has been heated to thequenching temperature, is immersed in the quenching oil contained in theprimary cooling bath 32 a so that the ring shaped article W can beprimarily cooled down to a temperature (for example, 290° C.) that ishigher than the martensitic transformation point (a primary cooling stepS2). At the secondary cooling station 33, the ring shaped article W,which has been primarily cooled, is immersed into the quenching oilwithin the oil bath 20 while deformation thereof is corrected by thedeformation correcting device 1, so that the ring shaped article W canbe secondarily cooled down to a predetermined temperature (for example,110° C.) (a secondary cooling step S3). At the post-cleansing station34B, the ring shaped article W, which has been secondarily cooled, istransferred to the subsequent processing step.

The induction heating device 50 employed at the preheating station 31 Aused in the practice of the third preferred embodiment is of a structureidentical with the induction heating device 50 employed at the heatingstation 31 used in the practice of the previously described secondpreferred embodiment and, therefore, the details thereof are notreiterated for the sake of brevity, but there is such a difference thatin contrast to the use of the induction heating device 50 at thepreheating station 31A according to the third embodiment for the purposeof heating by induction heating of the ring shaped article to thepredetermined preheating temperature near to the quenching temperature,the heating station 31 according to the previously described secondembodiment makes use of the induction heating device 50 for the purposeof heating to the quenching temperature. The structure and thedescription of the heating coil 52 shown in FIGS. 7A and 7B and FIGS. 8Aand 8B are also equally applicable to the third preferred embodiment ofthe present invention and, therefore, the details thereof are notreiterated for the sake of brevity.

As best shown in FIG. 9, the continuous heating furnace 31 a at thesoaking station 31B is a furnace for heating the ring shaped articles Wwhile the latter are transported successively in a row by a transportunit 31 b such as, for example, a conveyor within the interior of suchfurnace that is kept under a high temperature atmosphere.

Even in this third embodiment of the present invention, the processsteps subsequent to the primary cooling step S2 are identical with thoseemployed in the practice of the previously described first embodimentand the structure and the description of the ring shaped articledeformation correcting device 1 shown in FIGS. 2A and 2B are alsoequally applicable thereto and, therefore, the details thereof are notreiterated for the sake of brevity.

As described hereinbefore, according to the quenching apparatus 30 ofthe third embodiment of the present invention, since heating is effectedto the quenching temperature through the preheating station 31A, atwhich the heating takes place by means of induction heating, and alsothrough the soaking station 31B, at which the heating takes place bymeans of the continuous heating furnace 31 a, the ring shaped article Wcan be heated deep by induction heating in a matter of minutes with agood energy efficiency and, also, due to the use of the continuousheating furnace 31 a, the ring shaped article W in its entirety can besoaked. Since although the use is made of the continuous heating furnace31 a, the continuous heating furnace 31 a is used only for the purposeof heating the ring shaped article W, which has been preheated to atemperature near to the quenching temperature, to the quenchingtemperature, the heating time can be reduced considerably in contrast tothat required to heat from room temperature. Also, the path oftransport, through which the ring shaped article W is transported withinthe furnace, may be short and, therefore, the equipment can be reducedin size.

The deformation correcting device 1 according to any one of theforegoing embodiments of the present invention can be embodied in thefollowing modes.

[Mode 1]

A deformation correcting device for correcting a deformation occurringin a ring shaped article, which has been heated, while the heated ringshaped article is cooled, which device comprises a support table, onwhich the ring shaped article in a heated condition is placed; a pair ofreceiving rolls, which rollingly contact an outer peripheral surface ofthe ring shaped article on the support table; a press roll provided inopposition to the pair of the receiving rolls with the ring shapedarticle intervening therebetween; a press roll drive mechanism fordriving the press roll between an advanced position, at which the pressroll is urged against the outer peripheral surface of the ring shapedarticle, and a retracted position, at which the press roll is separatedaway from the outer peripheral surface of the ring shaped article; and apress roll rotating mechanism for rotating the press roll then urgedagainst the ring shaped article by the press roll drive mechanism.

[Mode 2]

The ring shaped article deformation correcting device as defined in Mode1 above, further comprising a roll interval adjusting mechanism foradjusting the interval between the receiving rolls.

[Mode 3]

The ring shaped article deformation correcting device as defined in Mode1 above, in which the length of time required to perform a deformationcorrection with the press roll urged against the outer peripheralsurface of the ring shaped article is within the range of 40 to 90seconds.

[Mode 4]

The ring shaped article deformation correcting device as defined in Mode1 above, in which the temperature of the ring shaped article at the timea deformation correction is initiated with the press roll urged againstthe outer peripheral surface of the ring shaped article is 20° C. to 50°C. higher than the martensitic transformation point.

[Mode 5]

The ring shaped article deformation correcting device as defined in Mode1 above, further comprising an oil bath for cooling purpose and adeformation correcting time cooling mechanism for immersing the ringshaped article into a quenching oil, contained within the oil bath, atthe time of deformation correction to thereby cool the ring shapedarticle.

[Mode 6]

The ring shaped article deformation correcting device as defined in Mode5 above, in which the deformation correcting time cooling mechanismcomprises a support unit for tiltably supporting the support table suchthat a ring shaped article support area of the support table, where thering shaped article is placed, may be lowered, and a tilting unit fortilting the support table supported by the support unit, so that whenthe support table is tilted by the tilting unit, the ring shaped articlecan be immersed into the quenching oil within the oil bath.

[Mode 7]

The ring shaped article deformation correcting device as defined in Mode1 above, in which the ring shaped article is a raceway ring of a bearingassembly.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings which are used only for the purpose ofillustration, those skilled in the art will readily conceive numerouschanges and modifications within the framework of obviousness upon thereading of the specification herein presented of the present invention.Accordingly, such changes and modifications are, unless they depart fromthe scope of the present invention as delivered from the claims annexedhereto, to be construed as included therein.

What is claimed is:
 1. A deformation correcting device to correct adeformation occurring in a ring shaped article, which has been heated,while the heated ring shaped article is cooled, comprising: a supporttable, on which the ring shaped article in a heated condition is placed;a pair of receiving rolls, which rollingly contact an outer peripheralsurface of the ring shaped article on the support table; a press rollprovided in opposition to the pair of the receiving rolls with the ringshaped article intervening therebetween; a press roll drive mechanismfor driving the press roll between an advanced position, at which thepress roll is urged against the outer peripheral surface of the ringshaped article, and a retracted position, at which the press roll isseparated away from the outer peripheral surface of the ring shapedarticle; and a press roll rotating mechanism for rotating the press rollthen urged against the ring shaped article by the press roll drivemechanism.
 2. The deformation correcting device as claimed in claim 1,further comprising a roll interval adjusting mechanism for adjusting theinterval between the receiving rolls.
 3. The deformation correctingdevice as claimed in claim 1, further comprising an oil bath for coolingpurpose and a deformation correcting time cooling mechanism forimmersing the ring shaped article into a quenching oil, contained withinthe oil bath, at the time of deformation correction to thereby cool thering shaped article.
 4. The deformation correcting device as claimed inclaim 3, wherein the deformation correcting time cooling mechanismcomprises a support unit for tiltably supporting the support table suchthat a ring shaped article support area of the support table, where thering shaped article is placed, may be lowered, and a tilting unit fortilting the support table supported by the support unit, so that whenthe support table is tilted by the tilting unit, the ring shaped articlecan be immersed into the quenching oil within the oil bath.